Primer composition for adhesive bonding and method of using the same

Abstract

Disclosed herein is a solvent-based bonding primer composition containing one or more organic solvents, one or more epoxy resins, one or more curing agents, a silane compound, and a low amount of core-shell rubber particles in nanometer size, submicron or micron size. Also disclosed is a method of applying the solvent-based bonding primer composition onto a metallic surface of a first substrate prior to bonding the metallic surface to a second substrate via a curable adhesive.

What is claimed is: 
     
       1. A surface treatment for treating a metallic surface prior to adhesive bonding comprising:
 applying a primer composition onto a metallic surface to form a curable primer film having a continuous surface, the primer composition comprising: 
 (i) one or more epoxy resins; 
 (ii) at least one amine-containing curing agent; 
 (iii) a silane compound having at least one hydrolyzable group; 
 (iv) core-shell rubber (CSR) particles; and 
 (v) a mixture of organic solvents comprising methyl ether ketone (MEK) in combination with at least one solvent selected from: diacetone alcohol (DAA), acetone, isopropyl alcohol, tetrahydrofuran (THF), ethylene glycol, xylene, toluene, and ethyl acetate, 
 wherein the primer composition has a solid content of 5%-30%, and the amount of CSR particles is less than 2 wt. % (weight percent) based on the total weight of the composition, 
 wherein water is not added to the primer composition, and 
 wherein components (i)-(v) in the primer composition form a homogeneous solution. 
 
     
     
       2. The surface treatment of  claim 1 , wherein the at least one amine-containing curing agent is selected from: aromatic diamines, dicyandiamide (DICY), and hydrazides. 
     
     
       3. The surface treatment according to  claim 1 , wherein the mixture of organic solvents consists of methyl ether ketone (MEK) and diacetone alcohol (DAA). 
     
     
       4. The surface treatment according to  claim 3 , wherein the weight ratio of MEK to DAA is from 60:40 to 95:05. 
     
     
       5. The surface treatment according to  claim 1 , wherein the CSR particles have particle size in the range of 10 nm-3000 nm. 
     
     
       6. The surface treatment according to  claim 1 , wherein the primer composition further comprises a corrosion-inhibiting compound. 
     
     
       7. The surface treatment according to  claim 1 , wherein the metallic surface is subjected to anodization or sol-gel process to form a metal oxide coating prior to applying the primer composition.